Previously, surface contours of manufactured parts or specimens have been measured using surface contacting methods such as a scanning stylus. Holographic methods which must be interpreted by a human observer have been described in the literature (see e.g. Optical Holography by R. J. Collier, C. B. Burckhardt, and L. H. Lin, Academic Press, 1971). These methods require either mechanical contacting or slow photographic chemical processing.
Recently issued U.S. Pat. No. 4,030,830 discloses a process and apparatus for sensing defects on a smooth surface. Although this patent uses similar components, a small region of fringes are formed where the fringes must be scanned over the surface to measure large surfaces. The system does not accurately characterize the surface in all three dimensional coordinates, nor does it utilize a computer controlled scanning system.